Re: [PATCH v4 05/11] block-coroutine-wrapper.py: default to main loop aiocontext if function does not have a BlockDriverState parameter

[Emanuele Giuseppe Esposito]

Am 21/11/2022 um 16:30 schrieb Kevin Wolf:
> Am 16.11.2022 um 13:22 hat Emanuele Giuseppe Esposito geschrieben:
>> Basically BdrvPollCo->bs is only used by bdrv_poll_co(), and the
>> functions that it uses are both using bdrv_get_aio_context, that
>> defaults to qemu_get_aio_context() if bs is NULL.
>>
>> Therefore pass NULL to BdrvPollCo to automatically generate a function
>> that create and runs a coroutine in the main loop.
>>
>> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> 
> It happens to work, but it's kind of ugly to call bdrv_coroutine_enter()
> and BDRV_POLL_WHILE() with a NULL bs.
> 
> How hard would it be to generate code that doesn't use these functions,
> but directly aio_co_enter() and AIO_WAIT_WHILE() for wrappers that are
> not related to a BDS?
> 

At this point, I would get rid of s->poll_state.bs and instead use
s->poll_state.aio_context. Then call directly aio_co_enter and
AIO_WAIT_WHILE, as you suggested but just everywhere, without
differentiating the cases.

Then we would have something similar to what it is currently done with bs:

if t == 'BlockDriverState *':
            bs = 'bdrv_get_aio_context(bs)'
        elif t == 'BdrvChild *':
            bs = 'bdrv_get_aio_context(child->bs)'
        elif t == 'BlockBackend *':
            bs = 'bdrv_get_aio_context(blk_bs(blk))'
        else:
            bs = 'qemu_get_aio_context()'

I haven't tried it yet, but it should work.

Thank you,
Emanuele